Patent document 1 discloses a device for attaching a nut to a pipe by attaching to the inner wall of a metal square pipe so as to tighten with screw from outside of the square pipe, by using a so-called self-piercing nut in which each nut punches a hole in a metal sheet, and the rim of this hole is crimped simultaneously and pressed into the side wall groove of the nut, and attached to the metal sheet.
The device disclosed in patent document 1 is a manual device, which has not been put in practical use so far in the conventional background.    Patent Document 1: Japanese Patent Application Publication No. 53-16394 (Japanese Patent No. 0943112)